1. Field of the Invention
An aspect of the invention relates to techniques of the communication via the network.
2. Description of the Related Art
In the communication via the network, there is an illegal communication between a web server and a client. For example, a technology for detecting the illegal communication is disclosed in Japanese Laid-open Patent Publication No. 2006-279930.
To implement unauthorized communication, there exist methods that use HyperText Transport Protocol (HTTP) that is used in transmitting and receiving data between a web server and a client. Since the HTTP is used by clients to access a web server, even in firewalls that are systems to prevent unauthorized communication, communication is permitted. Accordingly, by using the HTTP, the unauthorized communication can be realized through the firewalls. Since the procedures in the unauthorized communication are not disclosed, the procedures are not known.